Three “Fairy Pins”: Chaenotheca brunneola, Phaeocalicium polyporaeum, and Mycocalicium subtile

"Fairy Pins" growing on Phellinopsis conchata growing
on black ash (Fraxinus nigra).

I used to be able to count the number of hairs on a flea’s leg—with the naked eye. Not so much anymore. This age thing has got hold of me, has stolen the elasticity of the lenses of my eyes the same way it’s been slyly stealing elasticity from other parts of my body.

There’s no help for the rest of me, but for my fast-failing close-up vision, my new best friend is my loupe. Without this little magnifier I’d be lost. I’d have no idea if a mushroom’s stem was smooth or minutely velvety, or if its cap was finely hairy or tomentose.

These possible Chaenotheca brunneola 
are minute, less than 1mm long.

So when I brought home a new polypore I’d carved off a standing dead black ash—standing in 2 feet of snow, I might add—I used my loupe to have a close look at it. Pore surface pale yellow-brown with a blush of gray, small pores. Pileus black and cracked and partially covered in moss and algae, and…hey...what’s this? Black whiskers?! Nope, not whiskers, more like mini black matchsticks—and by "mini," I mean less than a millimetre long.

Though I’d never actually seen it, I was aware of the existence of a tiny black “Fairy Pin” fungus called Phaeocalicium polyporaeum that grows on old, often algae-covered polypores. So I looked it up. Turns out, though, that its substrate is limited to Trichaptum species, and my Fairy Pins were definitely not growing on a Trichaptum of any kind—more likely a Phellinus, specifically, Phellinopsis conchata. So what on earth were they?

Chaenotheca brunneola

It took a bit of detective work with the internet and a microscope to tentatively put a name to this serendipitous discovery: Chaenotheca brunneola.  

Spores of Chaenotheca brunneola(?)

Chaenotheca brunneola isn’t a simple ascomycete, as the Phaeocalicium is, but instead one that happens to live in partnership with a photosynthetic algae—in other words, it's a lichen. It has a shiny black stem, and a black head that usually has a fuzzy brown coating of spores. It grows most commonly on dead wood, of both conifers and deciduous trees, on lumber and fence posts…and, occasionally, on polypores. Cool. If that's what my collection is. Though mine have the expected globose spores, the heads are not shaped like pinheads; they're more elongated—like teeny weeny Trichoglossum. 

Phaeocalicium polyporaeum growing 
on Trichaptum biforme.

Phaeocalicium polyporaeum

Although I'm still not sure what these little guys are, they piqued my curiosity, so out I went into the snow again to look for old Trichaptum to see if any were hosting the Fairy Pin I'd already heard about, Phaeocalicium polyporaeum. 

Not fifty metres from my house, I found a tree covered head to toe in Trichaptum biforme. I inspected one with my loupe. Aha! There they were! I inspected more. Eighty percent were hosting Phaeocalicium. Who knew it would be so easy?

Phaeocalicium polyporaeum spores

Mycocalicium subtile grows on wood.

Mycocalicium subtile

But the story doesn’t end there. A day later I stumbled upon another bunch of Fairy Pins, these ones strewn along the length of a naked maple limb suspended above the snow. Assuming I’d simply found more Chaenotheca brunneola on its more usual substrate, I ignored the sample I’d brought home until I was about to photograph it a few days later. I got out my loupe expecting to see brown, fuzzy Chaenotheca heads. But that’s not what I saw. These ones had distinctly black heads that were quite large in proportion to their stems. I immediately plucked one off with my tweezers and squashed it under a slide cover, and—ta da—under the microscope it was clear that I’d found a third species.

Mycocalicium subtile spores

After more detective work, I found a third name, Mycocalicium subtile, another non-lichenized species like the Phaeocalicium. It grows on decorticated wood, usually in the open, hence its common name, "Snag Pin." Though I can't find any reference to this one ever colonizing old polypores, I did discover that there is yet another non-lichenized pin that does: Chaenothecopsis caespitosa. Since that Fairy Pin is as tiny as all the rest, the only way I'll ever find it is with my trusty loupe.

References:

Hutchison, L. J 1987: Studies on Phaeocalicium polyporaeum in North America. - Mycologia 79(5): 786-789

Lichens of North America, Irwin M. Brodo, Sylvia Duran Sharnoff, Stephen Sharnoff, Yale University Press, 2001, 828 pages, ISBN: 0300082495

John Plischke III’s Trial Key to Mushrooms That Grow on Other Mushrooms